This invention relates to a method for tagging a fish for identification purposes and, more generally, relates to a method of identifying fish.
As described in U.S. Pat. Nos. 3,128,744 and 3,545,405, small identifying tags implantable within the body tissues of macro-organisms such as fish are used for investigating the migratory habits of those organisms. Upon implantation of an identifying tag with coded information thereon, the organism is released to exist in its normal environment and is subsequently recovered along with a mass of organisms when they are removed from their normal environment. The tag is then excised from the organism's body tissues and the identifying data is deciphered and used for establishing research statistics. The statistics measure such parameters as population size, the rate of exploitation by commercial fisheries, the natural, i.e., non-fishery, mortality rate, migration routes, geographical limits to populations and genetic separation (as at spawning).
In the case that the identifying tag is completely contained within the body tissues of the organism, the tag can be retreived and read only by severely wounding or killing the host organism.
As described in U.S. Patent Application Ser. No. 740,193, filed May 31, 1985, an identifying tag may take such a form that the identifying information is carried on a portion of the tag outside the body tissues of the host organism. Although in the case of such an externally readable tag the host organism need not be sacrificed in order to retreive the identifying information, the externally visible tag has the disadvantage of possibly significantly modifying survival and other biological traits and behavior. In addition, percutaneous tags are frequently shed or otherwise lost.
In the case of completely internal identifying tags in the form of cylindrical stainless steel segments, implantation of the tags into respective organisms is implemented by first severing the segments sequentially from a continuous strand of wire and injecting them one by one into the respective organisms, as disclosed in U.S. Pat. No. 3,820,545 and U.S. patent application Ser. No. 916,165 filed Oct. 7, 1986. In accordance with the disclosures of those two documents and pursuant to universal practice in the fisheries industry, internal tags are implanted at locations deep within the body tissues of the host organisms and are visible, without manipulating the body tissues, only in extraordinary circumstances.
U.S. Pat. No. 3,313,301 is another patent directed to an instrument for implanting an identifying tag in a macro-organism such as a fish, while U.S. Pat. No. 4,233,964 discloses an identifying tag having a plurality of spaced grooves and apertures defining a code readable by x-ray equipment.